Our objectives are to: 1. Study the kinetic properties of converting enzyme, CE, from lung (bovine, human, rabbit, etc.). 2. Study the molecular properties of different enzyme forms. 3. Study the enzyme mechanism. 4. Prepare a chromogenic substrate for C.E. that can be used in a continuous assay with a spectrophotometer and recorder. 5. Prepare a substrate that is suitable for use as an activity stain in gel electrophoresis. 6. Develop an affinity chromatographic procedure for purification of the enzyme.